GDI with High-Performance 2-Stroke Application: Concepts, Experiences and Potential for the Future
Bibliographic record
Abstract
Thanks to its unsurpassed power-to-weight ratio, its low package space and low-maintenance design, the loop-scavenged two-stroke engine with conventional mixture preparation is still being used in some sectors of vehicle engineering, such as boat drives, snow mobiles and motor scooters, as well as in hand-held applications. To maintain the potential of the 2-stroke engine for the future it is necessary to take adequate steps against the system-dependent disadvantage of the simple 2-stroke engine, namely that of higher emissions compared to 4-stroke engines. One possible solution is gasoline direct injection. Its more frequent use will increase the production numbers, making it an interesting technology even in the above-mentioned cost-sensitive applications. The current report presents various concepts of direct injection in 2-stroke engines, from air-assisted injection through to high-pressure direct injection, and compares them with traditional techniques of mixture formation. The report describes the experiences with different direct-injection systems, in particular in high-performance engines, from their development up to series application, presenting both simulation results and measurement data from tests for illustration. It also deals with the feasibility of exhaust aftertreatment and with the particularly critical subjective assessment of smoke and smell. In-depth investigations using 3D-CFD were made to develop and examine the different combustion methods and injection systems, including spray and combustion simulations with CFD codes specially adapted for two-stroke engines, taking the movement of the specific two-stroke charge into account. Flow investigations were made to evaluate the simulation and were compared with the tests and the simulations by means of measuring techniques specially adapted for two-stroke engines. The report concludes with an outlook on the effects of gasoline direct injection on fleet emissions and with the evaluation of future gasoline direct-injection technologies as to their feasibility and potential.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.009 | 0.007 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".